Gallium nitride-based compound semiconductor device

ABSTRACT

An LED emitting light of wavelength mainly 375 nm or below. The LED includes a GaN layer ( 16 ), an n-clad layer ( 20 ), an AlInGaN buffer layer ( 22 ), a light emitting layer ( 24 ), a p-clad layer ( 26 ), a p-electrode ( 30 ), and an n-electrode ( 32 ) arranged on a substrate ( 10 ). The light emitting layer ( 24 ) has a multi-layer quantum well structure (MQW) in which an InGaN well layer and an AlInGaN barrier layer are superimposed. The quantum well structure increases the effective band gap of the InGaN well layer and reduces the light emitting wavelength. Moreover, by using the AlInGaN buffer layer ( 22 ) as the underlying layer of the light emitting layer ( 24 ), it is possible to effectively inject electrons into the light emitting layer ( 24 ), thereby increasing the light emitting efficiency.

TECHNICAL FIELD

The present invention relates to a gallium nitride (GaN)-based compoundsemiconductor device and, in particular, to a structure of a lightemitting element which primarily emits light in a wavelength band ofapproximately 375 nm or shorter.

BACKGROUND ART

LEDs having an InGaN light emitting layer and a wavelength band of 375nm-600 nm have been developed. In In_(x)Ga_(1-x)N, the wavelength ofemitted light varies when the proportion x of In is changed. Morespecifically, as the composition x of In is increased, the lightemission wavelength is shifted toward a longer wavelength side, from 363nm when x=0 (GaN) to 600 nm when x=1 (InN).

Recently, there have been active efforts to develop LEDs having a shortwavelength of 375 nm or shorter or having an ultraviolet (UV)wavelength. Demand for such short wavelength LEDs is very strong as theshort wavelength LEDs allow applications in, for example, a white lightsource in which the LED is combined with a fluorescent material orsterilization using the sterilizing characteristic of the LED. However,in an LED having an InGaN light emitting layer, in order to obtain alight emission wavelength of 375 nm or shorter, the composition x of Inmust be very small, resulting in a reduced fluctuation of In compositionand, consequently, significant reduction in a light emission efficiency.In addition, fundamentally, when InGaN is used as the light emittinglayer, light emission of wavelength of 363 nm or shorter cannot beachieved.

DISCLOSURE OF INVENTION

An object of the present invention is to provide a GaN-based compoundsemiconductor device having a superior light emission efficiencyprimarily in a wavelength band of 375 nm or shorter.

According to one aspect of the present invention, there is provided agallium nitride-based compound semiconductor device comprising aGaN-based light emitting layer formed above a substrate, wherein thelight emitting layer comprises a multilayer quantum well layer (MQW) inwhich an InGaN well layer and an AlInGaN barrier layer are layered. Aband gap of the AlInGaN barrier layer is wider than a band gap of InGaN,and an effective band gap of the InGaN well layer is widened so that thelight emission wavelength is shortened. In addition, by using AlInGaN asa barrier layer, a lattice mismatch between the AlInGaN barrier layerand the InGaN well layer is reduced, resulting in reduction indistortion and improvement in light emission efficiency.

According to another aspect of the present invention, it is preferablethat, in the gallium nitride-based compound semiconductor device, acompositional ratio of In in the InGaN well layer is, for example, 5% orgreater and 15% or smaller. According to another aspect of the presentinvention, it is preferable that, in the gallium nitride-based compoundsemiconductor device, a thickness of the InGaN well layer is, forexample, 1 nm or greater and 2 nm or smaller.

According to another aspect of the present invention, it is preferablethat, in the gallium nitride-based compound semiconductor device, acompositional ratio of Al in the AlInGaN barrier layer is, for example,14% or greater and 40% or smaller and a compositional ratio of In in theAlInGaN barrier layer is, for example, 0.1% or greater and 5% orsmaller.

According to another aspect of the present invention, it is preferablethat the gallium nitride-based compound semiconductor device furthercomprises an AlInGaN buffer layer adjacent to the light emitting layer.By providing an AlInGaN buffer layer adjacent to the light emittinglayer, it is possible to efficiently supply carriers into the lightemitting layer and improve the light emission efficiency.

According to another aspect of the present invention, it is preferablethat, in the gallium nitride-based compound semiconductor device, acompositional ratio of Al in the AlInGaN buffer layer is, for example,0.5% or greater and 40% or smaller and a compositional ratio of In inthe AlInGaN buffer layer is, for example, 0.1% or greater and 5% orsmaller.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a structure of an LED according to apreferred embodiment of the present invention.

FIG. 2 is a diagram showing a detailed structure of a light emittinglayer in FIG. 1.

FIG. 3 is a graph showing a relationship between a flow rate of TMAthrough a barrier layer and an output power.

FIG. 4 is a graph showing a relationship between a flow rate of TMAthrough a buffer layer and an output power.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention will now be describedreferring to the drawings and exemplifying a light emitting element, inparticular, an LED, as a semiconductor device.

FIG. 1 shows a structure of an LED according to a preferred embodimentof the present invention. An SiN buffer layer 12, a low temperature (LT)grown buffer layer 14, and an undoped GaN layer 16 are sequentiallyformed on a substrate 10 which is made of, for example, sapphire. Theselayers are provided in order to reduce dislocations. An n-GaN layer 18for reducing an operation voltage is formed on the undoped GaN layer 16.An SLS (strained layer Superlattice) in which a GaN and AlGaN arealternately layered (n-GaN/n-AlGaN) is formed on the n-GaN layer 18 asan n-clad layer 20. An AlInGaN buffer layer 22 and a light emittinglayer 24 are formed on the n-clad layer 20. As will be described below,the light emitting layer 24 comprises a multilayer quantum well (MQW) inwhich an InGaN well layer and an AlInGaN barrier layer are layered. AnSLS layer in which GaN and AlGaN are layered (p-GaN/p-AlGaN) is formedon the light emitting layer 24 as a p-clad layer 26. In other words, theLED according to the present embodiment has a structure in which theAlInGaN buffer layer 22 and the MQW light emitting layer 24 aresandwiched between the n-clad layer 20 and the p-clad layer 26. A p-GaNlayer 28 for reducing an operation voltage is formed on the p-clad layer26 and a p electrode 30 is formed on the p-GaN layer 28. A portion ofthe n-GaN layer 18 is exposed and an n electrode 32 is formed on theexposed region. Each layer is formed using an MOCVD method employing anMOCVD device.

In the related art, InGaN or the like is employed as the light emittinglayer 24. In the present embodiment, however, a multilayer quantum wellMQW in which an InGaN well layer and an AlInGaN barrier layer arealternately layered is used as the light emitting layer 24. In addition,the AlInGaN buffer layer 22 is formed adjacent to the light emittinglayer 24 when the light emitting layer 24 is sandwiched between then-clad layer 20 and the p-clad layer 26.

The light emitting layer 24 and the buffer layer 22 will now bedescribed.

FIG. 2 shows a structure of the light emitting layer 24 of FIG. 1. Thelight emitting layer 24 is formed by alternately layering an InGaN welllayer 24 b and an Al_(x)In_(y)Ga_(1-x-y)N barrier layer 24 a. Here, xand y are in the ranges of 0<x<1 and 0<y<1. The thickness of the InGaNwell layer 24 is, for example, 1.5 nm and the thickness of the AlInGaNbarrier layer 24 a is, for example, 12 nm. The pattern is repeated, forexample, 7 times, for a total of 14 layers. A band gap of the AlInGaNbarrier layer 24 a is wider than a band gap of the InGaN well layer 24b. When a forward bias is applied to the p electrode 30 and the nelectrode 32, electrons and holes combine in the InGaN well layer 24 band light is emitted. When a single layer of InGaN layer is employed, itis fundamentally impossible to realize a light emission of a wavelengthof 363 nm or shorter. By employing the MQW structure in which the welllayer and the barrier layer are alternately layered, it is possible towiden an effective band gap of the InGaN well layer 24 b. With thewidening of the effective band gap, light emission at a wavelength of363 nm or shorter can be enabled. Because a composition of In in theInGaN well layer 24 b which is the light emitting region is relativelyhigh (for example, composition x of In =10%) and fluctuation in Incomposition in the InGaN well layer 24 b is large, the light emissionefficiency is high. More specifically, when there is a spatialfluctuation in the composition, carriers are localized and the lightemission efficiency tends not to be reduced even when dislocations arecreated in InGaN.

In addition, because the Al_(x)In_(y)Ga_(1-x-y)N barrier layer 24 a alsocontains In (y>0), fluctuation in composition of In occurs. Thus,similar to the well layer 24 b, carriers are localized in the barrierlayer 24 a, resulting in inhibition of reduction in the light emissionefficiency regardless of the presence of dislocations. Upon comparisonbetween the AlInGaN barrier layer 24 a and an AlGaN barrier layer whichdoes not contain In, it can be seen that AlInGaN barrier layer 24 a hasadvantages that a lattice mismatch with the InGaN well layer 24 b issmall, lattice mismatch dislocations tend not to occur, andcrystallinity is high. Even when dislocations do not occur, withAlInGaN, distortions generated between the well layer 24 b and thebarrier layer 24 a can be reduced. When these layers are c-plane grownand a compression stress or a tensile stress is applied within theplane, an electric field is generated along a c-axis direction in ahexagonal crystal nitride semiconductor because of the piezoelectriccharacteristic. The generated electric field functions to move theelectron-hole pair supplied into the well layer 24 b in oppositedirections and reduces a spatial overlap of the wave functions of theelectrons and holes, resulting in a reduction in a rate ofrecombination. In other words, the light emission efficiency is reducedwhen there is a distortion in the well layer 24 b. This effect(quantum-confined Stark effect) is particularly significant when thewell layer 24 b is wide, but may also affect the well layer 24 b whenthe well layer 24 b is narrow. In the present embodiment, AlInGaN isused as the barrier layer 24 a to reduce the lattice mismatch andinhibit the distortion of the well layer 24 b. Because of thisconfiguration, a reduction in the light emission efficiency due to thequantum-confined Stark effect can be inhibited.

In this manner, by forming the InGaN well layer 24 b thinly in the lightemitting layer 24 and widening the band gap of the AlInGaN barrier layer24 a in the light emitting layer 24, the effective band gap of the InGaNwell layer 24 b can be widened through quantum effects such that a lightemission wavelength of 360 nm or shorter can be realized. In thisrespect, the LED of the present embodiment fundamentally differs from,for example, an LED which uses AlInGaN as a light emitting layer inplace of InGaN and which has a wavelength of 380 nm or shorter.

In an LED having a light emitting layer with InGaN as the light emittinglayer, the light emission efficiency is reduced when a thickness of theInGaN layer is 2 nm or smaller because the wave functions of theelectrons and holes confined in the well layer leaks to the barrier(that is, outside the well) and a contribution of recombination withinthe barrier becomes large. In the present embodiment also, the InGaNwell layer 24 b must be kept at a thin thickness of 2 nm or smaller (forexample, 1.5 nm) in order to cause the quantum effects, but thereduction in the light emission efficiency which occurs when the InGaNthin film is used as the light emitting layer does not occur in thelight emitting layer 24 of the present embodiment. Because AlInGaN isused as the barrier layer 24 a, the band gap of the InGaN well layer 24b is effectively widened and leak of the wave functions to the barrierlayer 24 a is reduced.

Because AlInGaN used in the barrier layer 24 a contains Al, the growthtemperature of AlInGaN must be a temperature (for example, 800° C.)which is higher than a growth temperature of InGaN (650° C.-750° C.). Inthis manner, by growing the layer at a temperature of 750° C. or higher,the crystallinity of the barrier layer 24 a is also increased.

The buffer layer 22, on the other hand, is formed by AlInGaN. Becausethe buffer layer 22 contains Al, the band gap is widened to a widthwhich is larger than that of the well layer 24 b which is InGaN. Usingthe layer 22, efficiency of supply of electrons into the well layer 24 bis improved and an amount of supply of holes to the buffer layer 22 isreduced so that the electrons and holes are efficiently confined withinthe well layer 24 b. An Al composition of the buffer layer 22 may beset, for example, to approximately 40%.

A method of manufacturing the LED shown in FIGS. 1 and 2 will now bedescribed in detail. The LED of the present embodiment is manufacturedthrough the following processes. In an MOCVD device under a normalpressure, a sapphire c-plane substrate 10 is placed on a susceptor in areaction tube and a thermal treatment is applied in a hydrogenatmosphere for 10 minutes at a temperature of 1100° C. Then, thetemperature is reduced to 500° C. Monomethyl silane gas and ammonia gasare introduced from gas introduction tubes for 100 seconds and an SiNbuffer layer 12 is grown on the substrate 10 in a discontinuous manner(or in an island-like manner). Then, a GaN buffer layer (LT bufferlayer) 14 is grown at the same temperature to a thickness of 25 nm bysupplying trimethyl gallium and ammonia gas through the gas introductiontubes. The temperature is then raised to 1075° C., trimethyl gallium andammonia gas are again supplied to grow an undoped GaN layer 16 to athickness of 2 μm. Next, an Si-doped n-GaN layer (n electrode layer) 18to which monomethyl silane gas is added is grown to a thickness of 1.0μm. A carrier density within the n-GaN layer 18 is approximately 5×10¹⁸cm⁻³.

Then, 50 pairs of Si-doped n-Al_(0.01)Ga_(0.9)N (2 nm) and Si-dopedn-GaN (2 nm) are grown at the same temperature to form an SLS structureand grow then-clad layer 20. As a material for Al, trimethylaluminum(TMA) is used. An average electron density of the n-clad layer 20 is5×10¹⁸ cm⁻³. Then, the temperature is raised to approximately 800° C.and an undoped Al_(0.05)In_(0.1)Ga_(0.94)N buffer layer 22 is grown. Athickness of the buffer layer 22 is 36 nm. Because the growthtemperature is low and 800° C., the resistivity is high. After theAlInGaN buffer layer 22 is grown, 7 pairs of undoped In_(0.1)Ga_(0.9)N(1.5 nm) and an undoped Al_(0.2)In_(0.1)Ga_(0.7)N (95 nm) are grown atthe same temperature of 800° C. to grow the MQW light emitting layer 24.A total thickness of the light emitting layer is 95 nm.

Then, the temperature is raised to 975° C. and 50 periods of Mg-dopedp-Al_(0.1)Ga_(0.9)N (2 nm) and Mg-doped p-GaN (1 nm) are grown to growthe p-clad layer 26 having an SLS structure and a p-GaN layer (pelectrode layer) 28 having a thickness of 20 nm is grown. Holeconcentrations of the p-clad layer 26 of the SLS structure and the p-GaNlayer 28 are respectively 5×10¹⁷ cm⁻³ and 3×10¹⁸ cm⁻³.

Table 1 shows structures, compositions, thicknesses, and growthtemperatures of the layers. TABLE 1 GROWTH LAYER STRUCTURE COMPOSITIONTHICKNESS TEMPERATURE p ELECTRODE LAYER p+−GaN 20 nm 975 p CLAD LAYERp−(GaN 1 nm/AlGaN 2 nm) Al: ˜10% 150 nm  975 50 SLS LIGHT EMITTING LAYERInGaN 1.5 nm/AllnGaN 12 nm WELL (In: ˜10%), 95 nm 800 (WELLLAYER/BARRIER 7MQW BARRIER(In: 1%, Al˜20%) LAYER) BUFFER LAYERSI-AllnGaN 36 nm In: 1%, A˜5% 36 nm 800 n CLAD LAYER n-(GaN 2 nm/AlGaN 2nm) Al: ˜10% 200 nm  1075 50 SLS n ELECTRODELAYER n-GaN  1 μm 1075UNDOPED GaN LAYER u-GaN  2 μm 1075 LOW TEMPERATURE LT-GaN 25 nm 500GROWN BUFFER LAYER SiN BUFFER LAYER SiN 500 SUBSTRATE SAPPHIRE

The numerical values in Table 1 are given as examples only, and othercombinations of values are also possible. For example, it is possible toemploy a structure in which 50 pairs of Si-doped n-Al_(0.1)Ga_(0.9)N(1.6 nm) and Si-doped n-GaN (1.6 nm) are grown to form an SLS structureas the n-clad layer 20, 20 nm of Al_(0.4)In_(0.01)Ga_(0.59)N is formedas the buffer layer 22, 3 pairs of In_(0.05)Ga_(0.95)N quantum welllayer (1.5 nm) and Al_(0.4)In_(0.01)Ga_(0.59)N barrier layer (10 nm) aregrown as the light emitting layer 24, and 50 pairs of Mg-doped GaN (0.76nm) and Al₀₁₃Ga_(0.87)N (1.5 nm) are formed as the p-clad layer 26. Thegrowth temperatures for growing the layers are also exemplary, and,therefore, the buffer layer 22 and the light emitting layer 24 mayalternatively be grown, for example, at a temperature of 840° C.

After the layers are sequentially grown in this manner, the wafer istaken out of the MOCVD device, Ni (10 nm) and Au (10 nm) aresequentially vacuum evaporated and formed on the surface, and a thermaltreatment is applied in a nitrogen gas atmosphere containing 5% oxygenat a temperature of 520° C. to form the evaporated metal film into a ptransparent electrode 30. Next, a photoresist is applied over the entiresurface and an etching process for forming an n electrode is appliedusing the photoresist as a mask. Ti (5 nm) and Al (5 nm) are vacuumevaporated on the n-GaN layer 18 exposed through the etching process anda thermal treatment is applied in a nitrogen gas atmosphere at atemperature of 450° C. for 30 minutes to form the n electrode 32. A goldpad for wire bonding having a thickness 500 nm is formed in a portion ofthe p electrode 30 and the n electrode 32, a rearside of the substrate10 is ground to a thickness of 100 μm, chips are cut through scrubbing,and the chips are mounted to obtain an LED device.

The LED device thus created was introduced into an integrating sphere, acurrent was supplied, and total light power emitted form the LED devicewas measured. The light power was approximately 1.6 mW at a suppliedcurrent of 20 mA. A light emission wavelength was within 360 nm±5 nm,although there was a slight variation on the wafer surface of a diameterof 2 inches.

Then, in order to confirm effects of the band gap of the AlInGaN barrierlayer 24 a in the light emitting layer 24, an LED device was createdwith only a flow rate of TMA (trimethyl aluminum) among the variousgases flowing during the growth of the barrier layer 24 a changed andthe light emission efficiency of the LED was examined.

FIG. 3 shows the results of this experiment. The x-axis represents aflow rate of TMA (in sccm) during growth of the barrier layer 24 a andshows a flow rate of gas to be supplied to the container in a relativeunit. The y-axis represents alight emission intensity in a relativeunit, which is approximately 1/4 of the value measured using theintegrating sphere. When the flow rate of TMA was increased from 7 sccmto 10 sccm, the light emission efficiency was increased to 2.6 times theoriginal light emission efficiency. Compositions of the barrier layer 24a grown with these conditions were approximately 1% for thecompositional ratio of In and approximately 20% for the compositionalratio of Al. Because the compositional ratio of Al is approximatelyproportional to the flow rate of the TMA, the compositional ratio of Alin the barrier layer 24 a is desirably larger than 14% (20×7 sccm/10sccm) from the viewpoint of the light emission efficiency. On the otherhand, when the compositional ratio of Al is too large, supply of currentbecomes difficult and the operational voltage is increased. Therefore,the compositional ratio of Al in the barrier layer 24 a has its lowerlimit defined by the light emission efficiency and its upper limitdefined by the operational voltage. Specifically, the compositionalratio of Al is preferably 14% or greater and 40% or smaller, and morepreferably 16% or greater and 40% or smaller.

Regarding the compositional ratio of In in the barrier layer 24 a,because the band gap is narrowed as the compositional ratio of Inincreases, the compositional ratio of In is preferably a small value.However, when the compositional ratio of In is zero, the light emissionefficiency is drastically reduced. This may be considered as due tofluctuations in composition of In occurring within the barrier layer 24a which contributes to improvement in the light emission efficiency.Therefore, the compositional ratio of In in the barrier layer 24 a has alower limit defined by the amount of compositional fluctuation and itsupper limit defined by the band gap. Specifically, the compositionalratio of In is preferably 0.1% or greater and 5% or smaller and morepreferably 0.1% or greater and 3% or smaller. Example of compositions ofthe barrier layer 24 a is Al_(0.4)In_(0.01)Ga_(0.59)N having acompositional ratio of Al of 40% and a compositional ratio of In of 1%.

When the compositional ratio of In in the well layer 24 b is too small,a fluctuation in In composition becomes too small and the light emissionefficiency is reduced. When, on the other hand, the compositional ratioof In in the well layer 24 b is too large, the light emission wavelengthis shifted towards a longer wavelength side. Therefore, an optimumcompositional ratio of In is determined based on the desired lightemission wavelength and the thickness of the well layer 24 b. Forexample, when the light emission wavelength is 360 nm, the compositionalratio of In in the well layer 24 b is preferably 5% or greater and 15%or smaller, and more preferably 5% or greater and 13% or smaller. Anexample of compositions of the well layer 24 b is In_(0.05)Ga_(0.95)Nhaving a compositional ratio of In of 5%. The thickness is preferably 1nm or greater and 2 nm or smaller in order to realize the quantum effectand is more preferably 1.3 nm or greater and 1.8 nm or smaller. Thepresent inventors have confirmed that, when the thickness of the welllayer 24 b is 3 nm or greater, the light emission wavelength is 400 nm.The grown temperature of the well layer 24 b and the barrier layer 24 ais preferably 750° C. or greater as described above, and is morepreferably 770° C. or greater (for example, 800° C.).

Next, the flow rate of TMA to be supplied during the growth of thebarrier layer 24 a in the light emitting layer 24 was fixed at 10 sccmwhile the flow rate of TMA to be supplied during the growth of theAlInGaN buffer layer 22 was varied, and changes in the light emissionefficiency were measured.

FIG. 4 shows the results of this experiment. In FIG. 4, the x-axisrepresents a flow rate of TMA in a relative unit. The y-axis representsan output power in a relative unit. When the flow rate of TMA wasincreased, the compositional ratio of Al in the buffer layer 22 wasincreased. When the flow rate of TAM was increased from zero to 3 sccm,the light emission intensity was increased to 2.7 times the originallight emission intensity. When the flow rate of TMA was increased to 10sccm, the light emission intensity was reduced. The light emissionintensity was low when the flow rate of TMA was zero because the bandgap of the buffer layer 22 is narrow (because the compositional ratio ofAl is 0) and, consequently, electrons cannot be effectively suppliedfrom the buffer layer 22 to the light emitting layer 24. Alternatively,it is possible to consider the reason for the light emission intensitybeing low when the flow rate of TMA is zero to be that the holes leak tothe buffer layer 22 and the confinement of holes within the well layer24 b is insufficient. The light emission efficiency is reduced also whenthe compositional ratio of Al is too large because the crystallinity isreduced and the band gap of the layer is too widened, resulting inreduction in the tendency for the electrons to be supplied from then-clad layer 20.

Therefore, the compositional ratio of Al in the AlInGaN buffer layer 22is preferably 0.5% or greater and 40% or smaller, and is more preferably1% or greater and 40% or smaller. Regarding the compositional ratio ofIn in the AlInGaN buffer layer 22, the present inventors confirmed thatthe light emission efficiency is drastically reduced when thecompositional ratio of In is zero. It can be considered that thisphenomenon is due to fluctuations in composition of In occurring in thebuffer layer 22 which contributes to improvement in the light emissionefficiency. Therefore, the compositional ratio of In in the AlInGaNbuffer layer 22 is preferably 0.1% or greater and 5% or smaller, and ismore preferably 0.1% or greater and 3% or smaller. An example ofcompositions of the AlInGaN buffer layer 22 isAl_(0.4)In_(0.01)Ga_(0.59)N having a compositional ratio of Al of 40%and a compositional ratio of In of 1%.

As described, in the present embodiment, a multilayer quantum wellstructure in which an InGaN well and an AlInGaN barrier layer havingpredetermined compositional ranges are alternately layered is employedas the light emitting layer 24 to widen the effective band gap of InGaNand allow light emission of 340 nm-375 nm. In addition, AlInGaN is usedas the barrier layer in order to improve the light emission efficiencyand an AlInGaN buffer layer 22 having predetermined compositions isprovided adjacent to the light emitting layer so that carriers can beeffectively injected and the light emission efficiency is improved.

A preferred embodiment of the present invention has been described. Thepresent invention, however, is not limited to the preferred embodimentand various modifications may be made.

For example, in the preferred embodiment, an SiN buffer layer 12 isformed. However, this SiN buffer layer 12 is provided for inhibitingdislocations and may be omitted as necessary.

Alternatively, it is also possible to replace the SiN buffer layer 12and the low temperature (LT) grown buffer layer 14 by a low temperaturegrown GaNP buffer layer.

1. A gallium nitride-based compound semiconductor device comprising: aGaN-based light emitting layer formed above a substrate, wherein thelight emitting layer comprises a multilayer quantum well layer in whichan InGaN well layer and an AlInGaN barrier layer are layered.
 2. Agallium nitride-based compound semiconductor device according to claim1, wherein a compositional ratio of In in the InGaN well layer is 5% orgreater and 15% or smaller.
 3. A gallium nitride-based compoundsemiconductor device according to claim 1, wherein a compositional ratioof In in the InGaN well layer is 5% or greater and 13% or smaller.
 4. Agallium nitride-based compound semiconductor device according to claim1, wherein a thickness of the InGaN well layer is 1 nm or greater and 2nm or smaller.
 5. A gallium nitride-based compound semiconductor deviceaccording to claim 1, wherein a thickness of the InGaN well layer is 1.3nm or greater and 1.8 nm or smaller.
 6. A gallium nitride-based compoundsemiconductor device according to claim 1, wherein a compositional ratioof Al in the AlInGaN barrier layer is 14% or greater and 40% or smaller,and a compositional ratio of In in the AlInGaN barrier layer is 0.1% orgreater and 5% or smaller.
 7. A gallium nitride-based compoundsemiconductor device according to claim 1, wherein a compositional ratioof Al in the AlInGaN barrier layer is 16% or greater and 40% or smaller,and a compositional ratio of In in the AlInGaN barrier layer is 0.1% orgreater and 3% or smaller.
 8. A gallium nitride-based compoundsemiconductor device according to claim 1, further comprising: anAlInGaN buffer layer adjacent to the light emitting layer.
 9. A galliumnitride-based compound semiconductor device according to claim 8,wherein a compositional ratio of Al in the AlInGaN buffer layer is 0.5%or greater and 40% or smaller, and a compositional ratio of In in theAlInGaN buffer layer is 0.1% or greater and 5% or smaller.
 10. A galliumnitride-based compound semiconductor device according to claim 8,wherein a compositional ratio of Al in the AlInGaN buffer layer is 1% orgreater and 40% or smaller, and a compositional ratio of In in theAlInGaN buffer layer is 0.1% or greater and 3% or smaller.
 11. A galliumnitride-based compound semiconductor device according to claim 1,wherein the InGaN well layer and the AlInGaN barrier layer are formed ata temperature of 750° C. or greater.